Koepfer beat de Minaur, a US Open quarter-finalist last week in New York, 3-6 6-3 7-6 (7-5) on the red clay in the Italian capital.

Koepfer faces a second-round showdown with French fifth seed Gael Monfils.

Earlier on Tuesday, Australian John Millman moved into the round of 32 in Rome with a hard-fought 7-5 7-6 (7-2) win over Portuguese lucky loser Joao Sousa.

His reward was a match-up with eighth-seeded Argentine Diego Schwartzman.

Three-time major winner Stan Wawrinka was sensationally beaten by 18-year-old debutant Lorenzo Musetti.

Qualifier Musetti, 17 years Wawrinka's junior, delivered a brilliant performance in Rome to win every game of the opening set before taking the second on a tie-break to secure a 6-0 7-6 (7-2) win.

Musetti, the world No.249, becomes the first player born in 2002 to win a match on the ATP Tour.

The Italian teenager, who was only three when Wawrinka made his debut in Rome 15 years ago, will play Kei Nishikori next.

World No.1 Novak Djokovic will start his Rome Masters campaign against Salvatore Caruso after the Italian qualifier beat American Tennys Sandgren 3-6 6-3 7-6 (7-4) on Tuesday.

Caruso, ranked 87th in the world, will not have much time to recover from his 2 hours and 51 minutes win over Sandgren because his tie with Djokovic will be second on Centrale Court on Wednesday.

Also on Tuesday, Russian ninth seed Andrey Rublev cruised through to the second round with a 6-4 6-4 win over Argentine qualifier Facundo Bagnis.

German Jan Lennard-Struff was defeated 6-1 7-6 (7-5) by Argentine qualifier Federico Coria, who will meet Italian fourth seed Matteo Berrettini in the next round.

Canada's Denis Shapovalov eased through by sweeping past Argentina's Guido Pella 6-2 6-3 and his second round opponent will be Spanish qualifier Pedro Martinez who overcame American Sam Querrey 6-3 7-6 (7-3).

Australian Associated Press